GANTZ

A pair of high school students, Kei Kurono and Masaru Kato, are hit by a subway train in an attempt to save the life of a drunk homeless man who had fallen onto the tracks. Following their deaths, Kurono and Kato find themselves transported to the interior of an unfurnished Tokyo apartment, where they meet Joichiro Nishi, a Gantz veteran, and other clueless participants. The pair soon realizes that they are not allowed to leave the apartment. At one end of the room there is a large black sphere known as "Gantz".